When a wireless carrier starts stocking accessories – like protective cases – for unreleased smartphones, it’s usually a good signal that the handset will soon go on sale through that carrier. T-Mobile USA may still be dealing with fallout from red-hot HTC HD2 sales that have left it struggling to keep up with demand, but that doesn’t mean Magenta isn’t already looking forward to the next best thing. That “thing,” apparently, will be the Google Nexus One. T-Mobile is reportedly starting to fill their stockrooms with protective cases for the N1 superphone, but the packaging hints at a rebranded version of the Google N1 coming to T-Mobile.

What’s interesting here is that the Nexus One cases don’t refer to the handset as the Nexus One. T-Mobile has been known to rebrand popular devices, and it seems they may be doing so with the N1. We know the cases are intended for the Nexus One, and not a rebranded HTC Desire, because of the white trackball on the bottom of the handset. For the record, the N1 has not yet been rebranded by a carrier – most opting instead to keep in line with Google’s marketing efforts to push their own-branded handset out to eager Android fans.

We’ll keep a close eye on developments with any rebranded T-Mobile Nexus One handsets. T-Mobile already sells Google’s smartphone under the Nexus One brand. Is it possible we’ll soon see a rebranded N1 from T-Mobile? Could the product mockup in the accessory packaging merely be placeholders for a T-Mobile Desire? We hope to know soon!